1. Field Of The Invention
This invention relates to phase separator modules and, more specifically, to cross-flow co-current phase separator modules for separating mixtures of particles, oil and water.
2. Background Of The Related Art
Industrial waste water often includes a multi-phase mixture of water, oil and suspended particles. A variety of techniques have been devised for separating the components of such suspensions, including filtration, centrifugation, extraction and sedimentation. The details of many of these techniques are well-known to those skilled in the art.
Gravitational separators utilize the force of gravity to induce sedimentation and agglomeration of the heavier components from the mixture, while the lighter components suspended in the mixture tend to coalesce, agglomerate and rise to the surface. The lighter phase is then removed from the surface by skimmers and other well-known techniques.
In order to enhance gravitational separation and coalescence, high surface area sieves and plates are placed in the flow of the fluid being separated. Generally the plates are welded or permanently attached to the sides of the separator tank. Waste water, however, can vary greatly in character. Often the contaminated waste water has large amounts of heavy oils and suspended solids which may adhere and block the sieves and plates of most oil/water separators. In such cases, the efficiency of the separator may not be a major consideration, but the ease of cleaning and replacement of the plates and filters is paramount. In other situations, the contaminated waste water may have a relatively high oil concentration with a low percentage of solids. In these situations, the efficiency of the separator may be a much more important factor than the ease of cleaning and blocking of the sieves and plates.
Generally, two impingement plate orientations may be found in phase separators. The first, called the countercurrent design, includes a plurality of parallel plates which are sloped at an angle, either upwardly or downwardly, in the direction of waste water flow. The plates, therefore, force the waste water to flow in the direction of the plates' slope either upwardly or downwardly. For example, when the plates are sloped upwardly, solids impinge on the top surface of the settling plates and slide down the plate due to the force of gravity against the flow of the waste water. When a second set of plates is used in series with the first, for example sloping downwardly, coalesced lighter phase oils and other constituents impinge upon the bottom surface of the plates and are forced to flow along the surface of those plates upwardly, against the flow of the liquid. Accordingly, the term countercurrent separation has been used to describe the process carried out in such a system. The disadvantage of the countercurrent separators is that the separated matter, either the lighter phase oils or the heavier phase solids are always travelling against the flow of the waste water, so that their progress is slowed. In addition, there is a higher tendency for turbulence and mixture of the phase flowing in the countercurrent direction. Another problem, which is more apt to occur in countercurrent separators, is clogging and agglomeration of heavy oils and solids on the surface of the plates.
A more efficient separator design is embodied in the cross-flow or co-current separators. These separators have their plates sloped normal to the direction of the flow. When several stacks of plates are used, the stacks are arranged in parallel rather than in series. The waste water to be separated enters the stack of sloped impingement plates and flows in a parallel fashion through the plates, never forced upwardly or downwardly, since the plates slope downwardly or upwardly in a direction perpendicular to the flow. Therefore, while the waste water being separated flows in a parallel fashion, the lighter phase material rises to the bottom surface of the upper impingement plates and is forced in the direction of the slope of the plates, while still flowing in the same direction of the flow. Likewise, the heavier phase material settles to the top surface of the lower impingement plates and follows the slope of the plate to the opposite side from the lighter phase material. Accordingly, both the heavy and lighter phase materials flow in the direction of the current of the waste water being separated, but in an opposite direction from each other across the surface of the plates. This type of separation process is therefore called cross-flow co-current separation. The co-current separators have the advantage of reduced turbulence and mixing of the lighter, and heavier phase components, since both components travel in generally the same direction of the waste water being treated. These separators, however, still suffer from clogging when the waste water has a large concentration of particulate matter,
One example of a countercurrent separator is described in U.S. Pat. No. 4,643,834. As illustrated in FIG. 2 of the '834 patent, the flow enters into a chamber containing a number of parallel plates arranged in series. The plates are in an inverted V configuration and slope upwardly, and then downwardly for each particular set of plates. The flow, thus enters from one side first travelling upwardly and then downwardly through the plates resulting in countercurrent separation. The central portion of the plates contain apertures to allow lighter components to float upwardly and each set of plates is separated by a gap to allow heavier liquids or solids to settle. The '834 patent includes a system to analyze the make-up of the discontinuous mixture which is fed into the separator, and a monitor controls both the separation space between the plates and/or the angle of attack of a particular plate. A separation between the plates may be adjusted by mechanical means as illustrated in FIGS. 11 and 12, and the angle of attack may be adjusted by electric motors as illustrated in FIG. 8. One disadvantage of this system is that the flow travels through the central gap portion and the gaps between each set of plates, causing remixing of the separated phase, either travelling upwardly or downwardly. In addition, the mechanical systems and the construction of the plate packs is complex, expensive and cannot be easily removed from the separator for cleaning or replacement of plates.
Another type of gravitational settler is disclosed in U.S. Pat. No. 3,563,389. This settler uses at least two stacks of sloping vertically spaced plates. At the sides of each of the plates are narrow vertical channels for the rising of lighter phase components and another channel for descending of heavier phase components. The stacks of plates, however, are permanently set into the separator, and cannot easily be changed or replaced. Another drawback of this settler is that the waste water flows through the vertical channels. This flow through causes turbulence and resuspension of rising and/or descending components.
Another separator is disclosed in U.S. Pat. No. 4,273,654 in which vertically sloped plates are arranged in a basin. Individual plates are grouped in subassemblies which are permanently fixed by draw bars or other arrangements. In addition, corrugated vertical plates are used to baffle off settling areas at the edges of the basin for descending materials, and at the center of the basin for ascending materials. Individual plates, however, cannot be easily removed from each subassembly for cleaning. In addition, individual plates cannot be changed to vary the spacing between the plates or the length of the plates. Rather, each subassembly must be removed and replaced with one having a larger or smaller spacing. Additionally, in order to obtain access to subassemblies positioned at the bottom of the separator, the top subassemblies must first be removed. Also, since the baffles are arranged parallel to the direction of the flow, the flow of waste water cannot be completely sealed off from the settling and rising zones. Another disadvantage of the system is that the baffles and mounting apparatus must be fixed to the sides of the separator tank. This arrangement does not offer flexibility and ease of maintenance and cleaning. In a related patent, U.S. Pat. No. 4,054,529 a cage assembly is disclosed which may be useful for holding the corrugated plates described in the '654 patent.
Other separator devices which utilize corrugated baffles are disclosed in U.S. Pat. Nos. 3,837,501, 3,666,112 and 3,666,111. None of these devices, however, allows the easy removal and replacement of individual plates for cleaning, for varying the distances between the plates, or for changing the length of the plates. Additionally, each of the separators disclosed, requires the mounting of the plates to the side walls of the separator tank.
Other types of separators are described in U.S. Pat. Nos. 4,194,976 and 1,709,676. The first is a gravitational separator with membrane baffles, such as rubber or other elastomers which are maintained in fixed separation and a metal frame. The membranes are separately attached to the supporting structure at a fixed distance, but the distance can be altered by changing the arrangement of ropes and pins holding the membranes. The patent does not, however, disclose the capability of changing the length of individual baffles. The second patent, U.S. Pat. No. 1,709,676 describes a pulp separator which includes vertical channels for settling or rising of lighter or heavier components, respectively.
Finally, U.S. Pat. No. 4,681,683 describes plate assemblies and individual collector troughs in the assembly. The plate assemblies can be removed for cleaning and maintenance. The spacing between the plates and the length of the plates, however, are fixed in the assemblies. Also, the apparatus can only be used for countercurrent separation.
Therefore, in order to solve the shortcomings in the prior art, it is an object of the present invention to provide a modular impingement plate design which may be used for either cocurrent or countercurrent separation.
Another object of the present invention is to provide such a modular plate design which allows for ease of removal and maintenance of individual plates within such modular design.
An additional object of the present invention is to allow the varying of the spacing between individual plates in a simple and cost effective manner.
A further object of the present invention is to provide a modular separator which allows the user to vary the plate lengths, the gap between the plates, or a combination of both in a simple and cost effective manner.
A still further object of the present invention is to provide a modular separator with quiescent zones for the settling of heavier phase material and the rising of lighter phase material without the turbulence associated with the prior art designs.